Method of grinding diamond-shaped recesses in metal-embossing roll



Jan. 15, 1963 l x7 l' E L. HOLLIS ETAL 3,073,690 METHOD OF INDING DIAMOND-SHAPED RECESSES METAL-EMBOSSING ROLL Filed April 7. 1960 l SPEED REDUCER (VARIABLE l /3Z f /7 'OO/001'@OIWWWWO/OOO000www Tia. 3.'

INVENTORS i@ ff wif 3,073,690 lVlETl-IOD OF GRINDING DIAMOND-SHAPED RECESSES 1N METAL-EMBUSSING ROLL Louis Hollis, Warren, and Ted J. Noider, Niles, Ohio,

assignors to Republic Steel Corporation, Cleveland,

Ohio, a corporation of New `lersey Filed Apr. 7, 1960, Ser. No. 20,618 2 Claims. (Cl. 51325) rIhe present invention relates to a method of grinding diamond-shaped recesses in a metal-embossing roll. More particularly, the present invention comprises a method of grinding a roll, which may later be used in rolling and embossing sheet metal as to form diamond-shaped recesses in the roll which will cause attractively decorative diamond-shaped raised portions on sheet metal, such as steel rolled by the roll in question. It may be desired that such embossing be done on both surfaces of a sheet of metal, in which case two such rolls may be used'and the metal rolled therebetween so as to emboss both surfaces simultaneously.

It is recognized that rolls for embossing sheet metal or for calendering relatively softer materials in sheet form have heretofore been formed with special patterns, so as to leave the sheet material suitably embossed after it has been rolled in contact with the rolls. Such special-shaped rolls have been formed in a large number of different Ways, some have been formed with recesses of various shapes to form correspondingly-shaped raised portions on the metal or oher material being rolled. The present invention provides, however, for the simple, rapid and effective grinding of such metal-embossing rolls in a. peculiar and novel way and bythe use of special apparatus hereinafter particularly described and claimed, so that a roll may be formed to provide diamond-shaped recesses therein in substantially the time and as simply as a roll could be dressed to assure a purely smooth, cylindrical surface, for example. Inasmuch as rolls for sheet metal and particularly for rolling sheet steel are usually large, heavy and of extremely hard material, in lorder to Withstand the type use for which they are intended, the only practical Way of forming recesses therein is by grinding or by acid-etching. The acid-etching process is, however, much slower and substantially more expensive, so that a grinding process, particularly in accordance with the novel features of the present invention, is much -t-o be preferred thereto.

Summarizing the present invention, therefore, it comprises rst suitably dressing 4a grinding wheel by cutting a helical groove therein by the use of a diamond or the like, so as to form a groove having a pitch in one direction as a right-hand pitch or right-hand screw thread; .then redressing the same grinding wheel i.e. the outer and generally cylindrical surface thereof by providing therein a helical groove or screw thread in a reverse direction for example a left-hand screw thread. These two superirnposed threads, which are preferably yof the same pitch, and are preferably of such a pitch that the grooves will be coincident at one portion only around the periphery of the grinding wheel, will result in leaving elongated diamond-shaped ridges on the surface of thegrinding wheel; or, considered from another point of view, these ridges would be diamond-shaped if they were visualized on a development of the outer and generally cylindrical surface of such wheel. With a grinding wheel so dressed, this grinding wheel is rotated with the ridges thereof in contact with the roll to be ground and with the grinding wheel rotating at a relatively rapid rate about an axis parallel to the axis of the roll. The roll is also rotated, but at a relatively slow rate. The grinding wheel is also m'oved axially, so as to engage the roll from one end to the other thereof, with this axial movement at such a rate ice that the grinding wheel is moved axially a distance at least equal to the width thereof for each complete rotation of the roll being ground. Thus the diamond-shaped portions ground in the roll during one rotation thereof will not overlap those ground during a succeeding rotation. It is then sometimes desired that the process be in effect repeated starting from either end of the roll to be ground, and mpving the grinding Wheel to the other end thereof, so vas to form a second -s'et of diamond-shaped recesses, which will preferably be located between those of the first set. This is a preferred embodiment of the invention.

This case as originally tiled included also a disclosure of a bluing process and apparatus for embossed sheet steel such as could be made using the special rollwith recesses ground therein according to the process of the present invention. The subject matter Aof this bluing process and apparatus has been divided out of the present application and is presented in a continuation-impart application of the same inventors, Serial No. 194,575, tiled May 14, 1962.

Other features and advantages of the present invention and details of the manner in which various portions .thereof are effected, as well -as equivalents at various stages of the entire process of this invention will be pointed out as the following description proceeds, this description being one coordinated with the accompanying drawings; in which FIG. 1 is a View from one edge looking toward the dressed grinding wheel in readiness for grinding diamondshaped depressions in a roll for rolling sheet metal;

FIG. 2 is a development of the outer, generally cylin-4 drical surface of the grinding wheel of FIG. l, on a somewhat enlarged scale, so that the details of this surface may be fully described; y

FIG. 3 is a fragmentary view in section on the linev 33 of FIG. 2 and on an enlarged scale showing the cutting surfaces or ridges remaining on the surface of the grinding wheel after it has been dressed in accordance with this invention;

FIG. 4 is a diagrammatic view showing the grinding wheel in the process of grinding depressions in a metalembossing roll and showing the roll partly ground during a lirst axial pass of the grinding wheel, means for rotating the roll and for rotating and axially moving the grinding wheel being shown diagrammatically;

FIG. 5 is a view similar to FIG. 4 showing the grinding process during a second or subsequent pass of the grinding wheel, the means for rotating the roll and for rotating and axially moving the grinding wheel being omitted; and

FIG. 6 is a fragmentary view similar to a portion of FIGS. 4 and 5 showing a part of a completed groundV surface of a metal-embossing roll with diiferently proportioned diamond-shaped recesses than those shown in FIGS. 4 and 5.

Referring to the drawings, and particularly to FIGS. 1 and 2, it is found that in order to prepare a grinding wheel by suitable dressing of the initially cylindrical surface thereof so as to grind the desired diamond-shaped recesses in a metal-embossing roll, it is necessary to bring the wheel into juxtaposition with a grinding wheel dressing element such as a diamond. This is normally done by holding the diamond stationary and rotating the grind# ing wheel, while moving it axially. This axial movement, coupled with the rotary movement of the grindingwheel and the impingement thereof with the diamond, results in cutting a helical groove in the originally cylindrical surface of the grinding Wheel'. The grinding wheel is rotated about lits axis and is traversed past the'diamond in one direction, so for example, as to cut a groove having a substantially right-hand thread, followed by asimilar traverse in the opposite direction, so as to cut an opposite or left hand thread, for example. It is of course immaterial whether the right hand or left hand thread be first cut, but it is a usual and preferred arrangement that the pitch of the right and left hand threads of the grooves cut by the diamonds in the surface of the grinding wheel shall be the same; and further, that the pitch be such that these grooves will intersect but once for each revolution of the grinding wheel. This will leave a plurality of elongate, substantially diamond-shaped ridges remaining as uncut portions of the originally cylindrical surface of the grinding wheel and with a portion of the periphery having no ridges whatsoever.

Thus, as shown in FIGS. 1, 2 and 3, there is illustrated a grinding wheel 15, which is mounted for rotation about the axis of a suitable shaft 16 and is arranged for axial movement in either direction by conventional means cooperating with the shaft 16 on which the lgrinding wheel is usually rigidly mounted. Such means are shown diagrammatically only in FIG. 4 of the accompanying drawings. The grinding wheel 15 is arranged for rotation by a motor M1, which is suitably connected thereto through appropriate mechanical power transmission means indicated by a broken line in FIG. 4. Similarly, the axial movement of the grinding wheel may be effected by a drive from this same motor through a variable mechanical speed reducer and any suitable mechanical means including, for example, a lead screw as shown diagrammatically in FIG. 4. The driving and axial moving means for the grinding wheel may be assumed to be conventional and of the type and character of those which have been used for many years in grinding rolls used in rolling metal such as sheet steel, wherein the grinding wheel is normally traversed axially during its rotation in order to grind a truly cylindrical surface on the roll being ground, the arrangement being generally illustrated diagrammatically in FIGS. 4 and 5. In these figures a metal-embossing roll is shown at 17, this roll being mounted for rotation about its axis and nomrally and usually being revolved during the grinding thereof by the grinding wheel 15, which is mounted for rotation about an axis parallel to the axis of the roll 17; so that at the end of the operation in accordance with the prior art, a roll having a truly cylindrical surface may be prepared. In a similar manner, the roll 17 is arranged to be rotated in the direction shown by the arrow in FIGS. 4 and 5 and by any appropriate driving or rotating means indicated in FIG. 4 diagrammatically as 4a motor M2, which is suitably connected by conventional mechanical driving means to rotate the roll 17. This apparatus may be essentially similar to or the same as apparatus used in the prior art for forming a desired surface, for example, a cylindrical surface on a metal-working roll. In such a prior art apparatus, the outer peripheral surface and the grinding wheel is usually truly cylindrical and is occasionally dressed by the use of a diamond as aforesaid so as'to maintain this truly cylindrical surface. The same apparatus used heretofore in the dressing of the grinding wheels and in the grinding of rolls to form purely cylindrical surfaces thereof may be used and is preferably used in accordance with the present invention, but with the particular changes hereinafter specically taught as to the manner inwhich the grinding wheel is prepared for the grinding operation and the relative rates of rotation of the several elements and axial movement of the grinding wheel to achieve the special results of this invention.

In FIG. 2 there is illustrated on an enlarged scale with respect to the scale of FIG. 1, a development of the outer originally cylindrical surface of the grinding wheel 15, which surface has been prepared by cutting thereinto the two opposite pitch angle grooves as aforesaid so as to leave a plurality of substantially diamond-shaped ridges shown at 18. It will be seen that at about the middle of the lengths (vetrically, as shown in FIG. 2) of the diamond-shaped ridges, i.e. about at the points where the section line 3 3 is indicated, the right and left hand thread grooves will be substantially coincident at 19. At these points, the ridges 18` will have their widest dimension in a direction axial of the grinding wheel 15. Thus, the edges 20 and 21 on one side of the upper portions of the diamond-shaped ridges 18 and on the other side of the lower portion thereof will be formed by margins of the right hand thread grooves; while the edges 22 on the other or left side of the upper portions of the ridges 18 opposite the edges 20 thereof and the edges 23 on the other or right side of the lower portions of these ridges opposite the edges 21 thereof will be formed by margins of the left hand grooves. At the intersections of the right and left hand grooves at 19 the edges will merge into one another as shown.

With the grinding wheel 15 prepared in this manner, the actual grinding of the roll is commenced, with the grinding wheel 15 arranged for rotation about an axis parallel to the axis of the roll 17 and with the grinding wheel starting at one end of the roll. The roll 17 is then rotated relatively slowly in the direction of the arrow shown at the right in each of FIGS. 4 and 5; while the grinding wheel 15 is rotated quite rapidly as hereinafter set forth about its axis and preferably in the direction of the curved arrows shown adjacent to the wheel 15 in FIGS. 4 and 5. During the continuous rotation of the grinding wheel 15 and the roll 17, the wheel 15 is moved continuously in an axial direction as indicated by the arrow 24 pointing to the left in FIG. 4.

As the surface of the grinding wheel other than the ridges 18 has been cut away by the preparatory treatment previously described, it will be understood that it is only these ridges 18 which will engage and grind portions of the roll 17. Furthermore, due to the fact that the roll is continuously rotated as shown, and as this rate of rotation is very much slower than the rotation of the grinding wheel itself, the initial contact of the ridges 18 will be at the points 25 of the ridges as shown in FIG. 2, which will form a series of points or narrow recesses in the initially cylindrical surface of the roll 17. As the grinding wheel 15 is rotating much faster than the roll 17, it will be seen that progressively wider portions of the grinding wheel will be coming into contact with portions of the roll 17. Thus, as the margins or edge portions 21 and 23 of the ridges 18 diverge progressively, wider and wider portions of the ridges will be effective to grind away portions of the roll 17. This divergence of the edges of the ridge portions reaches its maximum opposite the points 19, which provides for the widest portions of the diamondshaped recesses ground in the roll. From then on, and as both the grinding wheel 15 and the roll 17 continue to revolve, the edge portions 20 and 22 begin to converge toward one another, so that narrower and narrower portions of the ridges 18 will be coming into contact with the roll 17, thus forming the tapering portions at the upper ends of the several diamond-shaped recesses shown in FIG. 4, for example.

It will be understood of course, that the roll 17 is initially pretreated to give it a truly cylindrical surface prior to the cutting of the diamond-shaped recesses in this cylindrical surface. As shown in FIG. 4, in a substantially diagrammatic manner, but two diamond-shaped recesses are formed side by side during each complete revolution of the grinding wheel past a portion of the roll. This is actually only diagrammatic, for it will be understood, of course, that if a grinding wheel as shown in FIG. 2 where used, five such diamond-shaped recesses would be cut or ground in the surface of the roll during each rotation of the grinding wheel as there are five diamond-shaped ridges 18 shown in that ligure. In actual practice, however, the number of recesses cut by a single rotation of the grinding wheel may be considerably larger than ve as the present drawings are shown on a scale chosen to illustrate the principles of the invention, rather than to illustrate the apparatus on a scale similar to that in fact used in the practice of the present invention.

Referring now to FIG. 4, it will be noted that there are a plurality (two in this case) of diamond-shaped recesses shown at 26 cut duringV one revolution of the grinding Wheel then a similar plurality of diamond-shaped recesses 27 cut during a succeeding revolution of the grinding Wheel and so on. It will be further noted,V as indicated by the dashed lines 28 indicating the path of the surface of the grinding wheel past a portion of the surface of the roll 17, that the recesses 27 will be Ioffset from the recesses 26 in the direction of the arrow 24 incident to the axial movement of the grinding Wheel simultaneously with its rotation. Furthermore, it will be noted that in the normal course, the recesses 26 and 27 are not overlapping in a direction circumferential of the roll 17 for the reason that the ridges 18 do not extend around the entire periphery of the grinding wheel; but rather there is a circur'nferential space between the ends thereof as seen on the development of the surface of the wheel in FIG. 2, where no portion of the grinding wheel 15 will be in contact with the roll 17 being ground.

In order that there be reasonable control of the location of the diamond-shaped recesses and the frequency and spacing thereof, it is normal in the operation of this apparatus that the grinding wheel shall be moved axially a distance at least equal to the width of the grinding surface thereof, i.e. the axial Width, during each complete revolution of the roll 17. In this way, the recesses as 26 and 27 formed by the grinding wheel during one revolution of the roll 17, will not have superimposed thereon similar recesses formed during the next or a succeeding revolution of the roll 17 and while the grinding wheel is moving in a single direction, as in the direction of an arrow 24 from one end of the roll (as the right hand end, FIG. 4) to the other (as the left hand end thereof, as seen inthis gure). Thus, FIG. 4 illustrates the condition occurring while the grinding wheel 15 is moving from right to left and has moved something less than half the axial dimension of the roll 17. It is, of course, recognized that incident to the continuous axial movement of the grinding wheel, the recesses 26 and 27 will not be exactly rhomboidal in shape, but as this axial movement is relatively slight during the forming of any single diamond-shaped recess, and particularly is relatively slight in view of the quite large diameter of the roll 17 as hereinafter particularly set'out in actual examples, the recesses formed are substantially diamond shaped and may best be dened by this term, the exact geometrical shape of each recess closely approximating a rhombus.

It will be understood that itis possible to have the axial travel of the grinding wheel 15 some even multiple of the minimum travel thereof as aforesaid, which minimum travel is an axial distance equal to the width of the grinding wheel for each of the revolutions of the roll 17 Under these circumstances, the grinding Wheel could be operated so as to give a plurality of passes in grinding recesses covering the entire surface of the roll with a second pass, for example, eifectiverto grind recesses loca-ted in between the portions ground on the rst pass.

Another alternative which reasonably follows from the foregoing particular description is that the pitch of the grooves cut in the surface of the grinding Wheel might be a multiple or even a fraction of that actually used as disclosed hereinabove in FIG. 2, so that there would be two or more sets of diamond-shaped ridges, each generally similar to the ridges 18, and arranged more or less end to end around the periphery of the grinding wheel. In other words, the right hand and left hand grooves cut in the surface of the grinding wheel would intersect one another two or more times (each time as at 19) during each revolution of the grinding Wheel, rather than once as shown at 19, FIG. 2.

In any event, it is noted that there will normally be spaces around the periphery of the roll 17 between the ends of one set of recesses, as those numbered 26, and the beginnings of the next set, as those numbered 27. In order that the diamond-shaped recesses shall be more either in the same axial direction as the arrow 24 or in the opposite direction las particularly shown in FIG. 5 and indicated by an arrow 29. Under these circumstances, and with perhaps some cutting and trying in bringing the grinding wheel and the roll 17 into a desired grinding juxtaposition to one another, it will be found that ythe recesses of a second set shown at 30 and 31 will be arranged between lthe recesses of the first set, as generally indicated in FIG. 5, wherein the recesses of the second set are shown in the process of being formed during the axial movement of the grinding wheel 15 from left to right as seen in this figure. The helical path of contact of the grinding wheel with the roll during this second pass is bounded, for example by the dotted lines 32, FIG. 5.

Again, the degree of axial movement of the grinding wheel during this second or any subsequent pass is governed by the same principles as given above for the axial movement during the irst pass, i.e. the minimum laxial movement shall be a distance equal to the width of the grinding wheel 15 during each complete revolution of vthe roll 17. Again as aforesaid, the axial movement of the grinding wheel could be an even multiple of this minimum distance, with the intervening spaces later to be lled in between subsequent movement of the grinding wheel in the same or the opposite direction.

It has also been found that the lengths, in a circumferential direction measured around the roll 17, of the individual diamond-shaped recesses 26, 27, 30 or 31 can be adjustably controlled by a control of the relative speeds of rotation of the roll 17 and of the grinding wheel 15. Thus, if the grinding wheel is rotated slower with respect to the rate of rotation of the roll 17, relatively longer diamond-shaped recesses will result, for example, as in FIG. 6, by contrast with those of FIGS. 4 and 5. Relatively shorter diamond-shaped recesses can similarly be made by speeding up the grinding wheel with respect of the speed of the roll 17; or conversely, by 4slowing `down the speed of the roll with respect of the speed of the grinding wheel. The lengths of the diamond-shaped recesses will thus be understood to be a function of the relative speeds as aforesaid, rather than the absolute speed of either the grinding wheel or the roll.

The following examples can be given illustrating the practical carrying out of the-cutting of diamond-shaped recesses in accordance with the teachings herein given.

The grinding wheels used, at the start of their use, are about 36 in outside diameter and about 3" in axial width. As these grinding wheels are used, they are progressively reduced in outside diameter down to about 26. The rolls used may be of any desired diameter, for example, about 20 to 30 and are first ground to a truly cylindrical contour in a conventional manner. The axial dimensions of the rolls will depend upon the width of the sheets to be rolled thereby, but may be, for example, of a length to roll 36 wide sheets, which is one conventional size in the case of steel sheets such as have been treated in accordance with the present invention.

During the dressing of the grinding wheel 'by a diamond, it may be rotated at a speed of about 450 1.p .m. and moved endwise at the rate of about 72 inches per minute. The endwise movement is such that there will be about 19 to 20 thread turns in the 3" width of the grinding wheel, rather than the five shown lin FIGS. 2 Iand 3; or in effect two, as illustrated in FIGS. 4 and 5. Thus, in the actual use of this device about 19 or 2O diamondshaped ribs, each as shown at 18, will be present on the dressed grinding wheel and will cut this number of substantially parallel diamond-shaped `recesses in the roll simultaneously.

During the actual cutting of the diamond-shaped recesses in the roll, the grinding wheel may be operated at a speed in the order of magnitude of 900 to 1000 r,p.m., while the roll 17 is rotating at about 6 r.p.m. In a preferred embodiment of the invention, the endwise speed of the grinding wheel, i.e. in the direction of the arrows 24 or 29, is such that it will travel merely the width (axial dimension) of the grinding wheel, i.e. about 3 during a single complete revolution of the roll 17.

It will be recognized that the exact figures given herein are for purposes of illustration only, and are not intended to be limiting upon the particular practice of this invention, which may be variously predetermined from time to time in accordance with the general teachings herein contained.

By the practice of the method and the use of the apparatus as particularly herein disclosed, a series of relatively shallow diamond-shaped recesses is formed in the surface of a roll, each having a depth which is not atall critical as far as the present invention is concerned, but which may, for example, be of the order of magnitude of about 0.01 to about 0.02" in depth and is preferably about 0.015" in depth. Thus, metal rolled with a roll prepared in accordance with this invention will have raised embossed portions of generally diamondshape, which will be raised above the remaining surface of the metal by a height in the order of magnitude of about 0.003 to 0.02", and preferably about 0.015".

While there has been disclosed herein but one principal embodiment of the present invention, an attempt has been made as the description proceeded to point out alternatives for various features thereof, It is recognized that other alternatives and equivalents will occur to those skilled in the art from the foregoing particular disclosure. We do not wish to be limited, therefore, except by the scope of the appended claims, which are to be construed validly as broadly as the state of the' art permits.

What is claimed is:

1. The method of grinding diamond-shaped recesses in the surface of a metal-embossing roll, comprising the steps of dressing a substantially rigid grinding wheel having a generally cylindrical grinding surface by cutting in said cylindrical grinding surface a helical groove in the form of a right-hand screw thread, cutting a second helical groove in said grinding surface in the form of a left-hand screw thread, so that said grooves will intersect each other and leave ridges which are of elongated, substantially diamond shape in a development of said cylindrical grinding surface after dressing as aforesaid;

mounting said grinding wheel for rotation about an axis parallel to the axis of said metal-embossing roll, relatively slowly rotating said metal-embossing roll about its axis, relatively rapidly rotating said grinding wheel about its axis while maintaining it in grinding contact with the surface of said roll to be ground;

and relatively moving said roll and said grinding wheel in a direction axial thereof, so as to bring said grinding wheel successively and progressively into grinding contact with different parts of the surface of said roll incident to the relative axial movement between said grinding Wheel and said roll;

the relative axial movement of said grinding wheel and said roll being selected so that they will be moved axially a distance equal to the width in an axial direction of the initially cylindrical grinding surface of said grinding wheel during a single revolution of said roll.

2. The method of grinding diamond-shaped recesses in the surface of a metal-embossing roll in accordance with claim 1, in which for the forming of a first series of diamond-shaped recesses on the surface of said roll, said grinding wheel is moved from one end to the other thereof, said first series of diamond-shaped recesses being spaced from one another circumferentially of said roll; and comprising the additional step of forming a second series of diamond-shaped recesses in the surface of said roll in the manner similar to the forming of the first series thereof as aforesaid except that said second series of diamond-shaped recesses is formed so as to overlap the recesses of the first series in a direction circumfer ential of said roll and during the axial movement of said grinding wheel from one end to the other of said roll.

References Cited in the file of this patent UNITED STATES PATENTS 1,722,023 Streby July 23, 1929 1,989,792 Drader Feb. 5, 1935 2,082,734 Griffin et al Tune l, 1937 2,309,585 Haddock Jan. 26, 1943 2,418,535 Wild Apr. 8, 1947 2,453,709 Hughes et al Nov. 16, 1948 2,464,032 Franz Mar. 8, 1949 2,674,553 Shnitzler Apr. 6, 1954 2,729,919 Krafft Jan. 10, 1956 2,768,916 Seabold et al Oct. 30, 1956 

1. THE METHOD OF GRINDING DIAMOND-SHAPE RECESSES IN THE SURFACE OF A METAL-EMBOSSING ROLL, COMPRISING THE STEPS OF DRESSING A SUBSTANTIALLY RIGID GRINDING WHEEL HAVING A GENERALLY CYLINDRICAL GRINDING SURFACE BY CUTTING IN SAID CYLINDRICAL GRINDING SURFACE A HELICAL GROOVE IN THE FORM OF A RIGHT-HAND SCREW THREAD, CUTTING A SECOND HELICAL GROOVE IN SAID GRINDING SURFACE IN THE FORM OF A LEFT-HAND SCREW THREAD, SO THAT SAID GROOVES WILL INTERSECT EACH OTHER AND LEAVE RIDGES WHICH ARE OF ELONGATED, SUBSTANTIALLY, DIAMOND SHAPE IN A DEVELOPMENT OF SAID CYLINDRICAL GRINDING SURFACE AFTER DRESSING AS AFORESAID; MOUNTING SAID GRINDING WHEEL FOR ROTATION ABOUT AN AXIS PARALLEL TO THE AXIS OF SAID METAL-EMBOSSING ROLL, RELATIVELY SLOWLY REOTATING SAID METAL-EMBOSSING ROLL ABOUT ITS AXIS, RELATIVELY RAPIDLY ROTATING SAID GRINDING WHEEL ABOUT ITS AXIS WHILE MAINTAINING IT IN GRINDING CONTACT WITH THE SURFACE OF SAID ROLL TO BE GROUND; AND RELATIVELY MOVING SAID ROLL AND SAID GRINDING WHEEL IN A DIRECTION AXIAL THEREOF, SO AS TO BRING SAID GRINDING WHEEL SUCCESSIVELY AND PROGRESSIVELY INTO GRINDING CONTACT WITH DIFFERENT PARTS OF THE SURFACE OF SAID ROLL INCIDENT TO THE RELATIVE AXIAL MOVEMENT BETWEEN SAID GRINDING WHEEL AND SAID ROLL; THE RELATIVE AXIAL MOVEMENT OF SAID GRINDING WHEEL AND SAID ROLL BEING SELECTED SO THAT THEY WILL BE MOVED AXIALLY A DISTANCE EQUAL TO THE WIDTH IN AN AXIAL DIRECTION OF THE INITIALLY CYLINDRICAL GRINDING SURFACE OF SAID GRINDING WHEEL DURING A SINGLE REVOLUTION OF SAID ROLL. 